Well I have searched this forum through and through and have decided to post a thread in regards to a problem I have recently developed.

My car is a 2004 XJR with about 41,000 miles on it currently. Just this past weekend, I have developed either a bad knock or misfire issue. I have yet to figure out what it really is.

In the upper RPM ranges (5000-6100) in second gear and in mid to high RPM ranges (4500 - 6000) in third gear, the car will exhibit a type of clicking noise that emanates from the engine bay. Right before this noise occurs, there is a noticeable loss in power.

Yesterday, a "Restricted Performance" notification shot up on the cluster along with a blinking check engine light. After driving with this alert on, it went away by itself. Today, I have been running the motor hard just to see if anything is wrong and with each WOT run up to redline, the clicking noise will persist. I back off the throttle before the computer can tell me the car is about to explode though.

I have narrowed it down to being either:

1. Spark Plugs
2. Coil Packs
3. Failing bearings

I seriously hope that the problem will be corrected with either plugs, coil packs, or a combination of both.

To give you some more background on this issue. Yes, the motor has been borderline overheated. My shop forgot to bleed the cooling system which led to my temperature indicator to go into the red zone. "High Engine Temperature" never showed up on the dash though. After this incident, the needle climbed into the red area once again . I do not know how long it stayed there but after it did, I pulled off and blasted the heat until it went into the normal zone again. I replaced the thermostat shortly after and have no indicated overheating of the coolant since.

The motor has been regularly serviced with Mobil 1 at an interval of about 5000-7500 miles per change. Nothing else has been touched.

There is also a lot of valvetrain noise at idle.

Techs, would you give any insight into my situation on some possibilities on what may be the issue?

 

How about codes, got any to share?

 

I will be visiting Jiffy Lube tomorrow to see if any history codes are stored. If there are any, I will be sure to post them.


Hey Mark, I cleaned my MAF today with an entire bottle of cleaner. Initially I thought the problem had been almost alleviated, however, as soon as I got into third gear the car started to knock again. I guess it's time to check other things...thanks for the input though!

 

don't let the misfires continue long, you could damage the cats as a result. Codes are going to reveal much!

 

Well there are no stored codes in the history...

Hmm...maybe it is time to take it to the dealership and just have them deal with it.

 

let us know how you do, I'd be interested to know.

 

any feedback?

 

Note the age of the original post, (Oct 2010)

 

well,, i am desperate enough,,

 

Please post up your problem, and maybe someone will know something about it.